CHROMOSOME SURVEY OF SEALS IN THE BALTIC SEA IN 1988-1992

The populations of grey seals (Halichoerus grypus) and ringed seals (P hoca hispida botnica) in the Baltic Sea have decreased very much, espe cially during the last decades. Environmental pollution has been seen as an important cause. As top predators, the seals accumulate pollutan ts from their environment. High concentrations of chlorinated hydrocar bons and heavy metals have been found in seals from the Baltic Sea. In the present study the possible mutagenic effects of environmental pol lutants on the seals have been studied by screening cultured lymphocyt es for chromosome aberrations. Blood samples were taken from grey seal pups before weaning in March-April, and from adult ringed seals at th e end of April during 1988-1992. Blood cells were cultured for 48 h fo r screening for chromosome aberrations, and for 61 h with bromodeoxyur idine for the study of sister chromatid exchange (SCE). The types of a berrations found were chromosome and chromatid breaks, gaps, and fragm entations. More complicated rearrangements were rare. Blood samples fr om a total of 47 grey seal pups and from ten adult ringed seals were a nalysed. The mean frequency of cells with chromosome aberrations from the grey seals was 5.7% (SD+/-5.3). The median was 4, because the dist ribution was skewed with some animals having a considerably higher fre quency of aberrations than the average. Some cells with several aberra tions and fragmentation of the chromosomes were observed among the lym phocytes from these animals. The frequencies of SCEs were not markedly higher than those normally found in humans. The frequencies of aberra tions found in the adult ringed seals were lower than those found in t he grey seal pups. The chromosome aberrations are probably caused by c hemical pollutants.